Parenthesis

Parenthesis is the insertion of an aside into a sentence that is grammatically complete without it, set off by commas, dashes or brackets, so the reader hears a second thought cutting across the first.

The estimate (which nobody had checked) went out on the Friday.

Lift the aside out and the sentence is intact: The estimate went out on the Friday. That is the test, and it is what separates a parenthesis from a bound modifier, which cannot be lifted without changing the meaning.

What parenthesis means

The word comes from Greek and means roughly "a putting in beside". It has three senses, and they overlap.

1. The rhetorical figure. Inserting a word, phrase or whole sentence into a sentence that is grammatically complete without it. This is the sense this page is about.
2. The punctuation mark. In American English, parentheses are the round brackets ( ). British English usually just calls them brackets.
3. An interlude. In everyday speech, a parenthesis can be any aside or digression, as in a brief parenthesis in an otherwise busy week.

The adjective is parenthetical, and it is why a quick side remark in conversation is called a parenthetical comment. Screenwriters use the same word for something else: a parenthetical is the short direction in brackets under a character's name, telling the actor how to deliver a line.

Examples of parenthesis

My brother, who has never once been on time, arrived first. Why it works: the aside sets up the joke that the main clause delivers. Without it, arrived first is just information.

She would forgive him, she told herself, by morning. Why it works: three words of parenthesis put doubt into a sentence that would otherwise be a simple promise.

The house (it had been her mother's, and then nobody's) stood empty all winter. Why it works: a whole sentence of history fits inside the brackets without interrupting the plain fact around it.

He said he would be back by six (he was not). Why it works: the bracket is the narrator's comment, delivered flatly, and the flatness is the humour.

The money (and where else could it have gone?) was in the car. Why it works: a question can sit inside a statement. The question mark stays inside the brackets because it belongs to the aside.

The letter — and she read it three times — said nothing at all. Why it works: dashes make the aside the loudest part of the sentence, which is right here, because the rereading is the emotion.

Brackets, commas or dashes: choosing your punctuation

All three can mark a parenthesis, and they are not interchangeable. They work like a volume control.

• Commas: the quietest. The aside stays inside the sentence and barely slows it: The estimate, unchecked, went out on the Friday.
• Dashes: the loudest. The aside interrupts, and the reader hears the emphasis: The estimate — unchecked, of course — went out on the Friday.
• Round brackets: the most detached. The aside sounds like a remark made under the breath: The estimate (unchecked) went out on the Friday.

Square brackets are not for this. They mark an editor's insertion into someone else's words, as in a quotation.

A few mechanical rules:

• Close what you open. Commas and dashes come in pairs in the middle of a sentence. Open with a dash and you close with a dash, not a comma.
• Full stops go outside when the bracket is inside a sentence. When a whole sentence stands in brackets on its own, its full stop goes inside.
• At the end of a sentence, the full stop does the closing. He said he would call, eventually. No second comma needed.

Parenthesis in fiction

In first-person narration, the bracketed aside is characterisation in its own right. It gives you a narrator who is editing themselves in front of you, and a narrator who does that has something to manage. In close third person, an aside can let the character's own voice cut into the narration, which is a quick route into free indirect discourse.

In dialogue, people speak in parenthesis constantly, correcting and qualifying themselves as they go. Dashes are the usual mark there, because speech interrupts itself out loud.

Common mistakes

• The aside that swallows the sentence. If the parenthesis runs so long that the reader loses the main clause, it has failed, whatever marks surround it (see mid-sentence modifier). Fix: give the aside its own sentence.
• A missing closing comma. My brother, who has never once been on time arrived first. Fix: close the pair after time.
• Commas around information the sentence needs. Students, who cheat, will be expelled says that all students cheat. Without the commas, it says only the cheats will go. That is the difference between a parenthetical relative clause and a restrictive one.
• Brackets as a habit. One per paragraph starts to read as nervousness rather than voice. Save them for asides that earn the interruption.

Frequently asked questions

What is parenthesis in rhetoric?

In rhetoric, parenthesis is the figure of interrupting a sentence with a word, phrase or whole sentence that the grammar does not need. The main sentence still stands if you lift the aside out, as in 'My brother, who is never on time, arrived first.'

What does parenthesis mean?

It has three related meanings: the rhetorical figure of inserting an aside, one of the pair of round brackets used to mark such an aside, and, more loosely, any interlude or digression. The word comes from Greek and means roughly 'a putting in beside'.

What is the difference between parenthesis and parentheses?

Parentheses is the plural. In American English it usually means the pair of round brackets themselves. Parenthesis, singular, can mean one bracket or the figure of speech, and the figure can be marked with commas or dashes as well as brackets.

Should I use brackets, commas or dashes for an aside?

Commas keep the aside quiet and inside the sentence. Dashes make it loud and emphatic. Round brackets make it feel detached, like a comment made under the breath. Pick by how much attention you want the aside to get.